Radio Frequency Identification (“RFID”) tags are used for many purposes, including article control in retail stores and warehouses, electronic toll collection and tracking of freight containers. In many cases, the RFID tag is powered only by the electromagnetic energy from the radio signal sent by an interrogation device or “tag reader.” Thus, when the tag is not being read, it is not possible for the tag electronics to perform any functions unless the tag is also battery powered. Battery power is not an option in many cases for reasons such as cost, size and reliability.
RFID tags may have non-volatile memory for storage of information that the user or the tag issuing entity may need to change during the tag's lifetime. Changing or writing data to the non-volatile memory such as an EEPROM requires that the tag be powered. One application for the use of non-volatile memory in an RFID tag is to record events in the tag's environment, such as temperature, shock and vibration, to record the environment to which the object that the tag is associated with was subjected.
Passive tags are always “on” in that they respond any time when interrogated by RFID reader and are simple devices that only output information that is resident in memory, such as saved temperature data, tag ID number, etc. Also, tags only can output data using a single antenna, at a single frequency using only one protocol. In this regard, the tags are very limited in what can be outputted and the manner in which the data can be outputted.
For many applications, for example where tags are transported or carried by individuals through high traffic areas, (such as automotive tolling plazas, or security entrance points), there is currently no way to have a tag whose properties—protocol, or state, or ability to respond to the reader—can be changed externally by the tag owner, without using an RFID reader. Also, there is currently no way to change RFID reader settings remotely, using an RFID tag.